1. Field of the Invention
This invention relates to compositions containing granular inorganic oxidic materials which resist the adverse effects of high temperatures and which retain at temperatures above 500.degree. C. compressive strength. This invention is particularly directed to compositions containing a granular inorganic oxidic material which at temperatures above 500.degree. C. have increased compressive strength. This invention is also directed to the use of such compositions as plugs for tapping holes in vessels employed for metallurgical refining and in fabricated products, particularly those used in the construction industry, including partitions, facings and the like.
2. Discussion of the Prior Art
It is known to prepare moldings and compositions which consist of oxidic, inorganic additives, such as quartz gravel, quartz flour, or inorganic light substances such as expanded clay, expanded mica, expanded shale and so forth, and of a binder consisting of a thermoset such as phenolic resin, epoxy resin, polyester resin and the like, and which are used as building materials, in residential construction, for example. It has also been proposed to use these compositions in conjunction with tar binding agents as ramming compositions or as trough lining compositions and tap hole plugging compositions in metallurgical installations, e.g., for the lining of molds or of troughs.
The thermosetting and/or acid setting compositions that have become known hitherto on the basis of hard, granular, inorganic oxidic substances bound by phenolic resins, however, result in hardened products, for residential construction and for hardened linings and seals for metallurgical purposes, for example, which have a number of important disadvantages.
The organic binder in the hardened moldings or linings or seals has the property of becoming more or less completely pyrolyzed or coked or converted to ash under the prolonged direct action of flame or merely under the prolonged action of elevated temperatures. Even flame-resistant organic binding agents have this disadvantage. Accordingly, the fabricated products disintegrate more or less rapidly under the action of fire and/or heat, depending on the temperature and duration of such action, because the burning of the synthetic resin binding agent greatly diminishes or completely destroys their cohesion, i.e., their stability of shape, and their compressive strength.
The term "fabricated products" as used herein is to be understood to refer to construction materials such as partitions, facings and the like in home construction, and linings and seals for metallurgical installations, such as linings for troughs and molds as well as tap hole plugs and the like, in the hardened state.
To improve the stability of shape of hardened construction materials made from hard, granular inorganic oxide materials, especially porous ones, under the action of fire and/or high temperatures, it has previously been proposed to add alkali silicates, silicic acid esters, boric acids and their salts, triphenylborate, or other boron compounds which bind themselves to metal oxides under the action of heat and, in some cases, pressure, to mixtures containing phenolic resins, for example, as binding agents, before they are fabricated and hardened (German "Offenlegungsschrift"schrift" No. 1,571,399).
In these known construction materials, especially when porous hard materials are used as additives, it is disadvantageous that their compressive strength decreases under the action of heat and/or fire.
It is indeed possible to improve sound insulating properties by replacing the porous hard materials with non-porous hard materials as additives. By such measures the compressive strength of the hardened construction materials is improved. Nevertheless, it has hitherto been impossible to achieve the objective of replacing a partition built up by conventional methods of approximately 12.0 centimeter bricks with a partition approximately 3 to 5 cm thick having approximately the same heat and fire resistance and made of the previously known thermosetting and/or acid-setting compositions containing inorganic oxide additives and a binding agent of phenolic resin.
When hardenable compositions are used for metallurgical purposes, e.g., as compositions which can be rammed onto troughs or compositions for the lining of the inner surfaces of ingot molds or for tap hole plugging compositions, it is desirable to have sufficiently great stability of shape combined with compressive strength in the fabricated products under the action of heat or flame, as the case may be. The molten metals with which the compositions or fabricated products come into contact, in the tapping of a blast furnace for example, are usually at temperatures greater than 500.degree. C. up to about 1800.degree. C. The thermal stress is thus substantially greater than it is in a burning house, for example (in a residential fire the temperatures are generally reckoned at up to 800.degree. C., though the temperatures locally may be lower, e.g., below 500.degree. C.).
The fabricated products made from the known compositions, however, do not meet these requirements, since their compressive strength and their stability of shape are insufficient at the high temperatures involved.
The life of protective coatings in troughs or molds, when made from the compositions heretofore known, is relatively short. In most cases, cracking and spalling or partial decomposition is found after as little as a single use, so that the linings have to be renewed.
Especially problematical is the use of the previously known thermosetting compositions of the above-named type as tap hole plugging compositions. Tap hole plugging compositions have to meet particularly high requirements in practice. On the one hand, after they have set, they must withstand the high ferrostatic pressures and the relatively high temperatures (usually over 1000.degree. C. without disintegrating. They must shrink as little as possible. On the other hand, the plugs must be removable at the end of the smelting process. Consequently, they must not be excessively resistant to pressure. Thus, they must have maximum strength in order to withstand the pressures and temperatures prevailing in the metallurgical vessel.
Accordingly, it is an object of the present invention to provide a composition which can be employed in the construction industry which does not burn or disintegrate or lose its compressive strength substantially upon being subjected to temperatures, say, of 500.degree.-1000.degree. C. It is another object of the invention to provide a hardenable composition which can be used in the metallurgical industry as a ramming composition for troughs or as a liner for inner surfaces of ingot molds or as a plug for a tap hole, which composition does not disintegrate or substantially lose its compressive strength when subjected to temperatures of 500.degree.-1800.degree. C. It is a particular object of the invention to provide a hardenable composition whose compressive strength will increase when it is subjected to temperatures above 500.degree. C.